Failure in Composite Materials due to Volumetric Expansion of Freezing Moisture

Abstract

A model is developed for predicting volumetric expansion induced cracking in orthotropic composite materials due to freezing of trapped moisture in a slender rectangular flaw region. Conformal transformation and the complex function method are used to obtain the stress distribution in the matrix at the interior boundary. The stress field in the rectangular inclusion is derived by solving for two important variables characterizing the expanded equilibrium boundary determined by the principle of minimum strain energy. The compressive stress acting on the long side of the rectangular inclusion acts as a crack driving force., The model is used to predict the occurrence of cracking due to volumetric expansion of ice in a specific composite, EXTREN, that has been observed in experiments. The model can be adapted to predict fatigue life of composites under freeze-thaw conditions.